Medical Bionics - Theses

Permanent URI for this collection

Search Results

Now showing 1 - 1 of 1
  • Item
    Thumbnail Image
    Behavioural and objective measurements of listening effort
    CARABALI CARABALI, CARMEN ALICIA ( 2021)
    Listening effort has been defined as the mental effort exerted to understand auditory stimuli (Pichora-Fuller et al, 2016a). In many cases it is one of the causes of isolation and poor quality of life for people with hearing aids and cochlear implants. One way to mitigate this problem is to assess listening effort during the fitting of hearing devices and then use these measurements to optimise device settings to improve audibility while at the same time minimising listening effort. However, at the moment, clinical practice lacks a standardised protocol for the assessment of listening effort. In this project, a behavioural test for the assessment of task difficulty was developed and validated. As was the feasibility of using fNIRS for the assessment of listening effort. The first study in this thesis focused on the development and validation of a behavioural dual task test for assessment of task difficulty. The test consisted of identification of the last word of each sentence in lists of seven sentences each, and recall of those last words after the presentation of each list. The test was implemented with Australian speech material, to minimise possible confounding factors due to accent and dialect dissonances when applied to the Australian population. The test was applied to twenty-four normal hearing participants. The results showed that, both identification and recall scores could predict differences in difficulty between speech presented in noise and speech presented in noise in which a binary mask noise reduction algorithm was applied to the speech mixture. The implemented test could be used in the Australian research practice to compare different hearing devices and processing algorithms at high levels of speech intelligibility. The second study investigated the feasibility of using fNIRS for assessment of listening effort. More specifically, in this study fNIRS was used for identifying cortical neuronal biomarkers of listening effort in the left inferior frontal gyrus (LIFG) and bilateral posterior superior temporal gyrus (pSTG). The findings of the study suggest the existence of task related concentration changes of oxy- and deoxy- haemoglobin during the expected exertion of listening effort. Furthermore, when listening effort was modulated by manipulation of motivation and task demands, the change in concentration of oxyhaemoglobin, followed the behaviour expected for listening effort. However, the results of this study were not statistically significant due to the high level of uncontrolled variability on the data. These results suggest a potential for fNIRS in the assessment of listening effort, however, more investigation needs to be done to optimise the protocols for assessment of listening effort and improve effect size. The third study continued with the investigation of the feasibility of using fNIRS for the assessment of listening effort. However, in this study, rather than using fNIRS for monitoring cortical neuronal activity, it was used for monitoring concentration changes of total haemoglobin in the extracerebral compartment (scalp and skull), associated with the activation of the autonomic nervous system. The findings of this study suggested the existence of task related concentration changes of total haemoglobin in the extracerebral compartment. When compared with the expected behaviour of listening effort modulated by manipulation of motivation and task demands, it was found that the concentration changes of total haemoglobin in the extracerebral compartment followed the expected trend of behaviour of listening effort, but again, these results were not statistically significant. The results suggests that fNIRS could potentially be used for assessment of listening effort, not just due to the capability of monitoring cortical neuronal activity, but also due to the capability of monitor activation in the autonomic nervous system. In this project, behavioural and objective measurements of listening effort were investigated. The work reported in this thesis has shown that behavioural methods can be used for assessment of listening task difficulty. But also, the experiments reported in this thesis investigated the feasibility of fNIRS for the assessment of listening effort. It was determined that fNIRS has the potential for assessment of listening effort because it facilitates the study of its different aspects, associated with cortical neural activity, but also, with activation of the autonomic nervous system when listening under challenging conditions. This work provides a base for future research that should be focused in determining a protocol for measurement of listening effort that integrates cortical neuronal and systemic components extracted from the fNIRS signal to better understand listening effort.